Technical Note Patellar Tendon Lengthening: Rescue Procedure for Patella Baja Simone Perelli, M.D., Maximiliano Ibañez, M.D., Carlos Morales-Marin, M.D., Gabriel Acuña-Avila, M.D., Ricardo Espinoza-von Bischhoffshausen, M.D., Angel Masferrer-Pino, M.D., and Juan Carlos Monllau, M.D., Ph.D. Abstract: Patella baja is a challenging pathologic condition that causes pain and functional restrictions and can even lead to premature osteoarthritisdeven more so in cases of patella infera or cases associated with degeneration of the patellar tendon in which simple conservative treatment frequently is not resolutive. Several surgical options have been described for symptomatic patella baja: excision of the lower third of the patella, lengthening of the patellar tendon, reconstruction of the patellar tendon with allograft, and proximalization of the tibial tubercle. A combination of 2 or more of these treatments may be recommended in cases of significant patella baja. We present a simple and reproducible technique to address patella baja that combines a partial transposition of the tibial tubercle and patellar tendon lengthening using a subperiosteal patellar flap in continuity with the patellar tendon. P atella baja is defined as an abnormal low-lying patella that remains distal in relation to the femoral trochlea. It can affect patellofemoral tracking. patellar trauma, fractures around the knee,6 a chronic quadriceps tear,7 paralysis of the quadriceps, quadriceps dysfunction after poliomyelitis, or complex regional pain To evaluate patellar height, different techniques and syndrome.8,9 Furthermore, this condition can be measuring classifications are available.1-4 observed as an iatrogenic consequence of surgical When patella baja occurs, a shortening of the patellar procedures such as osteotomy,2,3 anterior cruciate tendon might be detected. This condition can be either ligament reconstruction, or total knee arthroplasty.10-14 congenital5 or acquired. The latter can be due to direct Postoperative patella baja is frequently associated with arthrofibrosis in the context of infrapatellar contracture syndrome.13,15 The resultant shortening of the tendon From Institut Català de Traumatologia i Medicina de l’Esport (ICATME)e might be due to either shrinkage of the tendon’s fibers Hospital Universitari Dexeus, Universitat Autònoma de Barcelona (S.P., M.I., or a mechanical adherence between the inner surface R.E-vB., A.M-P., J.C.M.), Barcelona, Spain; Department of Orthopaedic Surgery, Hospital Universitario de Cruces (C.M-M.), Barakaldo, Spain; of the tendon and the anterosuperior aspect of Department of Orthopaedic Surgery, Hospital de San Carlos (G.A-A.), San the tibia.10-15 Carlos, Chile; and Department of Orthopaedic Surgery, Hospital del Mar, As a result of this pathologic condition, patients may Universitat Autònoma de Barcelona (J.C.M.), Barcelona, Spain. complain of chronic anterior knee pain,4,16 weakness of The authors report the following potential conflicts of interest or sources of the extensor apparatus,2,3 and restricted range of funding: J.C.M. receives grant support from Spanish Ministerio de Economia, Industria y Competitividad (National Programme for Research Aimed at the motion.4,14,16 If this mechanically unfavorable Challenges of Society), and receives payment for lectures including service on condition is not properly addressed, a greater risk of speakers’ bureaus from Smith & Nephew and ConMed. Full ICMJE author development of premature osteoarthritis has also been disclosure forms are available for this article online, as supplementary observed.4,14 material. Conservative treatments of this pathologic condition Received July 7, 2019; accepted August 17, 2019. Address correspondence to Simone Perelli, M.D., Institut Català de Trau- include physiotherapy, systemic steroids, extracorpo- matologia i Medicina de l’Esport (ICATME)eHospital Universitari Dexeus, real shock wave therapy, and dry needling. Conserva- Universitat Autònoma de Barcelona, Carrer de Sabino Arana 5, 08028 tive treatments do not usually produce good responses, Barcelona, Spain. E-mail: perelli.simone@gmail.com especially in chronic cases. When conservative treat- Ó 2019 by the Arthroscopy Association of North America. Published by ment fails, surgical revision may be indicated. Several Elsevier. This is an open access article under the CC BY-NC-ND license (http:// creativecommons.org/licenses/by-nc-nd/4.0/). surgical options have been described for symptomatic 2212-6287/19851 patella baja. They include excision of the lower third of https://doi.org/10.1016/j.eats.2019.08.012 the patella,10 lengthening of the patellar tendon,16-20 Arthroscopy Techniques, Vol 9, No 1 (January), 2020: pp e1-e8 e1 e2 S. PERELLI ET AL. reconstruction of the patellar tendon with allograft,11,18 stop smoking for at least 6 months after surgery. In and proximalization of the tibial tubercle.2,20 addition, in the case of collagenopathy, chronic steroid A combination of 2 or more of these treatments may therapy, or hormonal alterations that can affect the be recommended in cases of significant patella baja tendon’s tissue quality, augmentation by means of an (e.g. Insall-Salvati index <0.5) or for relapse after pri- allograft should be considered. mary treatment. Preoperative evaluation should comprise magnetic Regarding patellar tendon lengthening, many tech- resonance imaging to assess tendon dimension and niques have been described. The superiority of one over quality as well as a lateral-view radiograph of both another has never been shown in terms of safety or knees to calculate the patellar height of the affected clinical outcomes. In every case, the technique to be knee to compare it with the unaffected side. A used should be technically easy, should be reproducible, computed tomography scan could be requested for and should allow for early postoperative mobilization to proper preoperative planning in cases of post-traumatic prevent joint stiffness and recurrence.21 The aim of this or congenital deformity of the inferior pole of the pa- study was to present a simple and reproducible way to tella or the anterior tibial tuberosity. Preoperative correct patella baja by means of a technique that planning should give us a precise idea of about how combines a partial transposition of the tibial tubercle many centimeters we should proximalize the patella. and patellar tendon lengthening using a subperiosteal patellar flap in continuity with the patellar tendon. Surgical Technique The patient is positioned supine, with a tourniquet inflated at the proximal third of the thigh. Lateral Indication and Preoperative Planning support is put in place, and a distal stop is used to hold Patella baja is defined by an Insall-Salvati index of less the lower extremity at 90 of flexion. An arthroscopic than 0.8 or a difference in the length of greater than evaluation of all the knee’s compartments is performed 15% in comparison to the contralateral side.2 A to establish whether any intra-articular problems lengthening of the patellar tendon is indicated in pa- contribute to lack of flexion and eventually to arthro- tients with symptomatic patella baja not responsive to scopically ablate fibrous scars. An anterior knee conservative treatment for more than 3 months (Fig 1). approach is subsequently performed from the proximal Contraindications are active infections, locally pole of the patella to the center of the tibial tubercle. aggressive rheumatic disease, and pathologic conditions The peritenon is sharply incised in its midline, creating that could negatively affect the healing of the tendon flaps that should be closed at the end of the procedure. such as inadequately compensated diabetes or vascu- After complete mobilization of the patellar tendon, it is litis. Smoking can also produce alterations in the micro- sized on the coronal plane and split into 2 halves equal vascularization processes. Therefore, patients should in width, from the inferior pole of the patella to the anterior tibial tuberosity (Fig 2). The lateral half is released proximally from the infe- rior pole of the patella, detaching the patellar perios- teum with an electric scalpel. Thus, a continuum of the patellar periosteum is created with the lateral bundle of the tendon, leaving its insertion at the tibial tuberosity intact. The lateral rein is then created (Fig 3). In the same way, the medial half is released from its distal insertion. In this case, the insertion of the tendon should be left intact, and a bone plug comprising all its fibers is harvested (Fig 4). On average, to achieve complete preservation of the enthesis, a bone plug of roughly 1  1.5  2 cm is created. First, the plug to be harvested is demarcated with an electric scalpel. Then, a hole is made in the center of the bone block with a 2.8- mm drill bit. Using an electric saw, we can start cutting over the previously marked border and finish detaching the bone plug with a chisel, avoiding fracturing both the harvested tissue and the anterior tuberosity. Fig 1. Intraoperative fluoroscopic evaluation of left knee with Once the bone plug is free, the proximal part of the patient in supine position. A patellar lengthening procedure medial rein is completely released from the medial, was performed for symptomatic patella baja not responsive to lateral, and deep adhesions, leaving its insertion intact conservative treatment. at the inferior pole of the patella. Osteophytes at the SURGICAL TREATMENT OF PATELLA BAJA e3 desired patellar height is seen to have been reached, lateral-view fluoroscopy with the knee in 90 of flexion should be performed to be sure that the right position has been achieved. A 2.8-mm drill bit is placed in the previously drilled hole, and it is drilled deeper into the tibia to mark its position. Decortication of the tibia around this hole is performed to a depth equal in size to the bone plug. The block is then fixed with a 3.5-mm cortical screw (Small Fragment System; DePuy Syn- thes) (Fig 6). Two convergent suture anchors (Osteoraptor, 2.9 mm; Smith & Nephew) are placed in the lower pole of the patella on its lateral side (Fig 7). A backstitch- Fig 2. Left knee in extension, viewed from above, with pa- style Krackow suture is made to fix the lateral rein at tient in supine position. The peritenon of the patellar tendon is incised in its midline, creating 2 flaps, and the tendon is split this level, with care taken to create a large contact area into 2 halves equal in width, from the inferior pole of the between the periosteal flap and bleeding cancellous patella to the anterior tibial tuberosity. bone. Both the medial and lateral reins should be fixed with the knee in 90 of flexion. Afterward, a fine adaptation inferior pole of the patella might be found. Careful and at the center of the tendon is performed with resorbable thorough removal is required before proceeding to the No. 2-0 interrupted suture (Vicryl; Ethicon) to join the next steps. Doing so will facilitate subsequent tendon 2 reins together (Fig 8). Range of motion is then veri- reinsertion thanks to decortication of this area. fied under fluoroscopy prior to closure. If adequate In accordance with our preoperative planning, we can tension and complete range of motion are achieved, the now proceed to lengthening the tendon: The medial rein is moved proximally and the lateral one is moved distally, both the same distance (Fig 5). Once the Fig 4. Left knee flexed 90 , frontal view, with patient in su- Fig 3. Left knee flexed 90 , frontal view, with the patient in pine position. The medial rein includes the medial half of the the supine position. The lateral rein includes the lateral half of patellar tendon and a bone block of at least 1  1.5  2 cm the patellar tendon in continuum with a periosteal flap ob- harvested in continuum with the patellar tendon from its tained from the lateral half of the patella. insertion at the anterior tibial tuberosity. e4 S. PERELLI ET AL. chronic (>1 year) lack of flexion is present, we suggest starting with continuous passive motion while keeping a peridural catheter in place for the first 48 hours to manage the pain and the reflex contraction. Limited range of motion between 0 and 90 is allowed for the first 2 weeks after the intervention. Isometric strengthening of the quadriceps and hamstring muscles is also recommended starting in the first few days after the procedure. Full weight bearing is allowed but only with a brace locked in full extension. We recommend leaving the same brace on overnight for the first 2 weeks after surgery to achieve better pain manage- ment and avoid sudden movements during sleep. The brace for weight bearing can be discontinued after 4 weeks if good muscular control has developed. After the first month, rehabilitation focuses on restoring full range of motion and strengthening the lower-limb musculature. Pivoting and strenuous activities are not recommended for the first 3 months. Moreover, athletic activity should be limited to light sports until 6 months postoperatively. Discussion Patella baja is a challenging pathologic condition that causes pain and functional restrictions and can even Fig 5. Left knee flexed 90 , frontal view, with patient in su- lead to premature osteoarthritis.4,14,16 So far, a gold pine position. In accordance with our preoperative planning, the medial rein of the patellar tendon is moved proximally and the lateral one is moved distally, both the same distance to lengthen the tendon symmetrically. peritenon is closed with a No. 4-0 continuous suture (Vicryl). A drain is left in place, and suturing of the wound is carried out. In case of a high risk of recurrence or poor-quality soft tissues, an allograft can be used for biological augmentation. Achilles tendon is suggested in these cases. A bone block is obtained that is sized to precisely fit and fill the bone gap left from the proximal trans- lation of the tibial bone block. The bone block of the allograft is inserted in a press-fit manner in the afore- mentioned defect and further blocked with a malleolar screw (Compact Ankle Fracture System; DePuy Syn- thes) (Fig 9). The soft part of the Achilles tendon is then fixed with a No. 0 absorbable suture (Vicryl) over the lengthened patellar tendon up to the quadriceps tendon while maintaining it in tension. The knee is finally immobilized in a brace locked in full extension. A step-by-step summary of the technique is shown in Table 1. Table 2 provides pearls and pitfalls for per- forming this surgical procedure. The whole technique is described in detail in Video 1. Rehabilitation Protocol Fig 6. Right knee flexed 90 , anterolateral view, with patient Controlled continuous passive motion is started in supine position. The bone block of the medial rein of the within the first few hours after the intervention. If patellar tendon is fixed with a 3.5-mm cortical screw. SURGICAL TREATMENT OF PATELLA BAJA e5 Fig 7. (A, B) Left knee flexed 90 , medial view, with the patient in the supine position. Two convergent suture anchors are placed in the lower pole of the patella on its lateral side to strongly fix the lateral rein. standard for surgical treatment of this pathologic tendon, reconstruction of the patellar tendon with condition does not exist, but multiple techniques have allograft or autograft, and transposition of the tibial been described in the literature. Excision of the lower tubercle are among them.2,11,20 Sometimes, third of the patella, lengthening of the patellar Fig 9. Lateral-view radiograph of right knee postoperatively. When augmentation with allograft is performed, the bone Fig 8. Left knee flexed 90 , frontal view, with patient in su- block of the allograft is inserted in a press-fit manner in the pine position. A fine adaptation at the center of the tendon is bone defect remaining after harvesting of the bone block of performed with resorbable No. 2-0 interrupted suture to join the medial rein. The bone block of the allograft is further the 2 reins together. blocked with a malleolar screw. e6 S. PERELLI ET AL. Table 1. Step-by Step Patellar Tendon Lengthening Step Description 1 The patient is positioned supine on the operating table, with 90 of knee flexion, using a distal foot support and a lateral support for the thigh. 2 An arthroscopic evaluation of the knee is performed to establish whether any intra-articular problems contribute to lack of flexion and eventually to arthroscopically ablate fibrous scars. 3 An anterior knee approach is performed from the proximal pole of the patella to the center of the tibial tubercle. 4 The peritenon is sharply incised in its midline, creating flaps that should be closed at the end of the procedure. 5 The tendon is split into 2 halves on the coronal plane equal in width. 6 The lateral half is released proximally from the inferior pole of the patella, detaching the patellar periosteum with an electric scalpel and leaving its insertion at the tibial tuberosity intact. 7 The medial half is released from its distal insertion, harvesting a bone block of roughly 1  1.5  2 cm, leaving its insertion at the inferior pole of the patella intact. 8 Osteophytes at the inferior pole of the patella should be removed, achieving complete decortication of this area. 9 In accordance with our preoperative planning, we can length the tendon: The medial rein is moved proximally and the lateral one is moved distally, both the same distance. 10 The bone block of the medial rein is fixed with a 3.5-mm cortical screw after decortication of the area. 11 Two convergent suture anchors are placed in the lower pole of the patella on its lateral side to fix the lateral rein. 12 A fine adaptation at the center of the tendon is performed with resorbable No. 2-0 interrupted suture to join the 2 reins together. 13 If adequate tension and complete range of motion are achieved, the peritenon is closed with No. 4-0 Vicryl suture and the approach is closed in the usual manner. a combination of several of the aforementioned periosteal flapecancellous bone contact point should be techniques is required. wide and bleeding. Thus, we are able to minimize the Our technique is a valid option to exploit both the possibility of failure of the reinserted rail. advantages of tendon lengthening and the transposition One advantage of our technique is that by leaving of the tibial insertion of the tendon itself. Doing so, we both the proximal and distal insertions of the tendon can take advantage of the full length of the patellar partially intact, the construct is solid and well vascu- periosteal flap that makes it possible for us to increase larized. For this reason, the healing process is safe and the patellar tendon height up to 3 cm. At the same time, quick. It even allows for immediate movement of the we can produce the same amount of proximalization of knee and load bearing as tolerated. Moreover, in that half of the tibial anterior tuberosity using a bone block way, we do not change the Q angle at all, which is also that leaves the new insertion on the tibial side very important in patellofemoral tracking.22 These points solid. could be issues with other techniques such as complete The weak point of the technique could be the rein- osteotomy of the anterior tibial tubercle that presents sertion at the inferior pole of the patella, made by su- the possibility of nonunion or an iatrogenic change in ture anchors. Attention should be paid to the direction the Q angle.23 Furthermore, our technique does not of the anchors inserted. They should be convergent and require any autografts and needs few and inexpensive have an adequate bone bridge in between. The devices to fix the tendon. Table 2. Pearls, Pitfalls, and Risks Pearls Preoperative evaluation should comprise MRI to assess tendon dimension and quality as well as a lateral-view radiograph of both knees to calculate the patellar height of the affected knee in comparison to the unaffected side. Once the desired patellar height is seen to have been reached, lateral-view fluoroscopy with the knee in 90 of flexion should be performed to prove it. Both the medial and lateral reins should be fixed with the knee in 90 of flexion to avoid any hypertension. If chronic lack of flexion is present, we suggest starting with continuous passive motion while keeping a peridural catheter in place for the first 48 hours. Pitfalls and risks Smoking can produce alterations in the micro-vascularization processes. Therefore, patients should stop smoking for at least 6 mo after surgery. The anchors implanted in the patella can fail if not correctly placed. They should be convergent and with an adequate bone bridge in between. The periosteal flapecancellous bone contact point should be wide and bleeding. The surgeon should pay attention to harvesting a sufficient bone block from the anterior tibial tuberosity to maintain all the fibers of the medial rein of the tendon intact. Pivoting and strenuous activities are not recommended for the first 3 mo. Athletic activity should be limited to light sports until 6 mo postoperatively. MRI, magnetic resonance imaging. SURGICAL TREATMENT OF PATELLA BAJA e7 Table 3. Advantages and Limitations Advantages The solid fixations allow early postoperative mobilization to prevent joint stiffness and recurrence. The healing process is safe and quick because of the solid and well-vascularized structure achieved. In case of collagenopathy, chronic steroid therapy, or hormonal alterations that can affect the tendon’s tissue quality, augmentation with an Achilles tendon allograft could be performed. The Q angle is not changed. This guarantees good patellofemoral tracking. The diameter of the tendon does not decrease significantly. It is easy to precisely calculate the amount of proximalization, and it is possible to increase the patellar height up to 3 cm. Both the proximal and distal insertions of the tendon are left partially intact. Limitations Only patients with severe pain and limitation of range of motion with no improvement during 3 mo of nonsurgical treatment are candidates for the described treatment. Aggressive rheumatic diseases, decompensated diabetes or vasculitis, and heavy smoking are not suitable indications. The surgical approach over the patellar tendon may lead to scar tissue formation between the subcutaneous tissue and the tendon itself. If augmentation with an allograft is performed, the cost of the technique increases. Moreover, differently from other techniques, the final 5. Ficat P, Hungerford D. Disorders of the patellofemoral joint. diameter of the tendon does not decrease significantly Baltimore: Williams & Wilkins, 1977. in comparison with the preoperative one and the inci- 6. Mariani PP, Del Signore S, Perugia L. Early development sion of the tendon we suggest is in line with the of patella infera after knee fractures. Knee Surg Sports Traumatol Arthrosc 1994;2:166-169. direction of the fibers themselves. These points also 7. Hockings M, Cameron JC. Patella baja following chronic guarantee good mechanical capacity of the newly built quadriceps tendon rupture. Knee 2004;11:95-97. tendon. 8. Mayr HO, Stoehr A. Komplikationen arthroskopischer Finally, given that the aim of the surgical procedure is Eingriffe am Knieglenk. Orthopade 2016;45:4-12 [in to return the patella to its normal height, this technique German]. makes it possible for the surgeon to easily calculate the 9. van Bussel CM, Stronks DL, Huygen FJPM. Complex amount of proximalization to be carried out intra- regional pain syndrome type I of the knee: A systematic operatively to restore patellofemoral tracking and knee literature review. Eur J Pain 2014;18:766-773. range of motion. The main advantages and disadvan- 10. Chonko DJ, Lombardi AV Jr, Berend KR. Patella baja and tages of the described technique are listed in Table 3. total knee arthroplasty (TKA): Etiology, diagnosis, and In conclusion, the described technique is a valid op- management. Surg Technol Int 2004;12:231-238. 11. Yoo JH, Chang JD, Seo YJ, Baek SW. Reconstruction of a tion for anterior knee pain and decreased range of patellar tendon with Achilles tendon allograft for severe motion due to patella baja. Although the technique is patellar inferada case report. Knee 2011;18:350-353. not technically demanding, all steps should be carefully 12. Jawhar A, Sohoni S, Shah V, Scharf HP. Alteration of the performed to avoid any risk of failure. patellar height following total knee arthroplasty. Arch Orthop Trauma Surg 2014;134:91-97. Acknowledgment 13. Paulos LE, Wnorowski DC, Greenwald AE. Infrapatellar The authors thank Mr. Eric L. Goode for his help with contracture syndrome. Diagnosis, treatment, and long- English-language correction. term followup. Am J Sports Med 1994;22:440-449. 14. Weale AE, Murray DW, Newman JH, Ackroyd CE. The length of the patellar tendon after unicompartmental and total knee replacement. J Bone Joint Surg Br 1999;81: References 790-795. 1. Insall J, Salvati E. Patella position in the normal knee 15. Paulos LE, Rosenberg TD, Drawbert J, Manning J, joint. Radiology 1971;101:101-104. Abbott P. Infrapatellar contracture syndrome. An unrec- 2. Drexler M, Dwyer T, Marmor M, Sternheim A, ognized cause of knee stiffness with patella entrapment Cameron HU, Cameron JC. The treatment of acquired and patella infera. Am J Sports Med 1987;15:331-341. patella baja with proximalize the tibial tuberosity. Knee 16. Bruhin VF, Preiss S, Salzmann GM, Harder LP. Frontal Surg Sports Traumatol Arthrosc 2013;21:2578-2583. tendon lengthening plasty for treatment of structural pa- 3. Ahmad CS, Kwak SD, Ateshian GA, Warden WH, tella baja. Arthrosc Tech 2016;5:1395-1400. Steadman JR, Mow VC. Effects of patellar tendon adhe- 17. Guido W, Christian H, Elmar H, Elisabeth A, Christian F. sion to the tibia on knee mechanics. Am J Sports Med Treatment of patella baja by a modified Z-plasty. Knee Surg 1998;26:715-724. Sport Traumatol Arthrosc 2016;24:2943-2947. 4. Caton J, Deschamps G, Chambat P, Lerat JL, Dejour H. 18. Jeong JS, Wang JH. Treatment of patella infera by patellar Patella infera. Apropos of 128 cases. Rev Chir Orthop Rep- tendon lengthening and augmentation with tibialis ante- aratrice Appar Mot 1982;68:317-325 [in French]. rior tendon allograft. Knee 2014;21:605-608. e8 S. PERELLI ET AL. 19. Dejour D, Levigne C, Dejour H. Postoperative low patella. 22. Dickschas J, Harrer J, Bayer T, Schwitulla J, Strecker W. Treatment by lengthening of the patellar tendon. Rev Chir Correlation of the tibial tuberosity-trochlear groove dis- Orthop Reparatrice Appar Mot 1995;81:286-295 [in French]. tance with the Q-angle. Knee Surg Sports Traumatol Arthrosc 20. Caton JH. The management of patella infera in current 2016;24:915-920. practice. Eur J Orthop Surg Traumatol 2010;20:365-371. 23. Payne J, Rimmke N, Schmitt LC, Flanigan DC, 21. Caton JH, Dejour D. Tibial tubercle osteotomy in patello- Magnussen RA. The incidence of complications of tibial femoral instability and in patellar height abnormality. Int tubercle osteotomy: A systematic review. Arthroscopy Orthop 2010;34:305-309. 2015;31:1819-1825.