Management of First-Time Patellar Dislocations

■ sports medicine update

MICHAEL GEARY, MD; ANTHONY SCHEPSIS, MD

dislocation usually present Merchant or axial views of Patellofemoral instability represents a continuum of with a reduced patellofemoral both knees. These studies abnormal patellofemoral joint mechanics, ranging from joint and a history of feeling should be reviewed for osteo- infrequent subluxation to recurrent dislocation. their knee “go out of place.” On chondral fracture and adequacy examination, a large hem- of patellofemoral joint reduc- arthrosis is typically present, tion. Consideration should also with tenderness over the medi- be given to magnetic resonance he average annual inci- The typical mechanism of al femoral epicondyle and imaging (MRI), which is more Tdence of first-time patella injury is external rotation of the medial border of the patella, in sensitive for osteochondral dislocation is 5.8 per 100,000.1 tibia with concomitant contrac- addition to pain with lateral injury and can also aid in diag- When risk is stratified by age tion of the quadriceps. Less fre- translation of the patella. nosis, given a characteristic set and gender, the risk of first-time quently, glancing blows to the Arthrocentesis should be con- of MRI findings seen with dislocation is highest in females patella may produce a disloca- sidered in the acute setting for patellar dislocation. These aged 10-17 years. In this group, tion. Factors that predispose to both patient comfort and to findings include disruption of the annual incidence of first- dislocation include an allow for a more accurate phys- the medial patellofemoral liga- time patella dislocation is 33 increased quadriceps angle, ical examination. ment and osteochondral bone per 100,000.1 trochlear dysplasia, patella alta, The typical lesion associat- bruises or fractures involving Stability of the patello- vastus medialis obliques atro- ed with lateral patella disloca- the inferomedial patella and femoral joint against lateral dis- phy, insufficient medial tion is injury to the medial lateral femoral condyle.3-5 location is based on osseous patellofemoral ligament, genu patellofemoral ligament.3-5 Treatment recommenda- constraint in Ͼ30° of flexion recurvatum, increased femoral Associated injuries frequently tions for first time patellar dis- and medial soft-tissue restraints anteversion, external tibial tor- include osteochondral frac- locations are controversial. Our in the early flexion range where sion, foot pronation, increased tures, and less frequently medi- practice has been to manage instability usually occurs. The patellar tilt, and patellar hyper- al collateral ligament (MCL) first time patellar dislocations medial patellofemoral ligament mobility. With greater anatomic sprain, anterior cruciate liga- nonoperatively, unless a dis- is the most important of these predisposition, the force ment (ACL) injury, and menis- placed osteochondral fracture medial soft-tissue restraints.2 required to dislocate the patella cal injury.3-5 Initial manage- or asymmetric reduction of the decreases. ment consists of immobilizing dislocated patella is noted From Boston University Medical the affected knee in extension. when compared to the normal Center, Boston, Mass. EVALUATION AND Radiographic evaluation knee. In the latter two cases, Reprint requests: Anthony MANAGEMENT should include anteroposterior arthroscopy is performed and Schepsis, MD, Doctor’s Office Bldg, Ste 808, 720 Harrison Ave, Boston, Patients having sustained a (AP), lateral, and tunnel views the knee is surveyed. Smaller MA 02118. first-time traumatic patella of the affected knee and displaced osteochondral frag-

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patient had a large effusion in the knee and Merchant views of both left knee and pain with minimal knees were obtained. A displaced range of motion. An arthrocentesis osteochondral fragment could be was performed and 120 cc of san- seen on the Merchant and lateral guineous fluid with fat globules views of the left knee (Figure 1). was removed. Crepitus was noted The left patellofemoral joint was with range of motion. The patient reduced and symmetrical in was able to perform a straight leg appearance with the right raise. The knee was stable to varus patellofemoral joint. and valgus stress at 0° and 30°. Magnetic resonance imaging of Lachman and anterior and posterior the left knee demonstrated an effu- drawer tests were negative. The sion and a midsubstance tear of the patient reported tenderness along medial patellofemoral ligament. In the medial patella border and medi- addition, a displaced osteochondral al femoral epicondyle. Pain fracture measuring 2 cm in diame- 1 occurred with lateral translation of ter, involving the lateral femoral the patella. Significantly increased condyle, was present. The ACL, Figure 1: Case 1. Merchant view demonstrating a displaced osteochondral fracture. asymmetric lateral patellar transla- MCL, posterior cruciate ligament ments that are not amenable to fixation are excised; larger fragments are fixed in an arthroscopic or open fashion depending on the size and location of the injury. If indicated, tears of the medial patellofemoral ligament are repaired primarily in an open fashion.

CASE REPORTS Case 1 A 16-year-old high school foot- ball defensive back sustained a first-time lateral dislocation of the left patella during a tackling drill in practice. The patient recalled sud- den knee pain after twisting his knee in the drill. He was diagnosed by the athletic trainer as having a lateral patellar dislocation. This was reduced on the field by extend- ing the injured knee and applying a medially directed force on the dislocated patella. The patient’s left 2 knee was then placed in extension Figure 2: Case 1. Arthroscopic picture demonstrating reduction of the displaced osteochondral fracture to the lateral in a knee immobilizer. femoral condyle. On evaluation the following day, the patient reported no history episode. The patient was otherwise tion was noted at 30° of flexion. (PCL), lateral collateral ligament of patella dislocation or instability healthy. Radiographs, consisting of AP, (LCL), and medial and lateral in either knee prior to the current On physical examination, the tunnel, and lateral views of the left menisci were intact.

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TABLE Summary of Studies on Treatment of Acute Patella Dislocation

Study Sample Mean Recurrence Study Design Treatment Size Follow-Up Surgical Technique Outcome Rate (%) Cofield7 Retrospective Conservative 35 11.8 y NA 91% satisfied 44 1977 Hawkins6 Retrospective Conservative 20 40 mo NA 50% moderate/ 15 1986 severe pain Cash8 Retrospective* Conservative 69† 8 y NA 52% G to E 43 1988 34‡ 75% G to E 20 Garth9 Retrospective Conservative 69 2 y NA 78% satisfied 26 1996 Maenpaa10 Retrospective Conservative 100 13 y NA 37% no complaints 44 1997 Dainer13 Retrospective Surgery 29 25 mo Scope, scope + LR 83% G to E 27% with 1988 LR, 0% no LR Vainionpaa14 Prospective Surgery 55 2 y Medial repair +/- LR 80% G to E 9 1990 Avikainen15 Retrospective Surgery 14§ 6.9 y Augment of MPFL 86% G 7 1993 Harilainen12 Prospective Surgery 53 6.5 y Medial repair/reef +/- LR 60% satisfied 17 1993 Sallay16 Retrospective Surgery 12 36 mo MPFL repair +/- LR 58% G to E 0 (33% sublux) 1996 Ahmad11 Retrospective Surgery 8 3 y VMO, MPFL repair + LR 96% satisfied 0 2000 Nikku17 Prospective, Conservative 55 2 y NA 70% G to E 30 1997 randomized Surgery 70 Proximal realignment 70% G to E 20 Fithian1 Prospective Conservative, 64࿣ 2-5 y Scope 9%, stabilize 12% NA 49 Scope 6%, stabilize 5% 17 نsurgery 125 2004

Abbreviations: E=excellent, G=good, LR=ligament repair, MPFL=medial patellofemoral ligament, NA=not applicable, and VMO=vastus medialis obliquus. *2 groups. †Predisposed. ‡Normal. §Chronic and acute. ࿣History of patellofemoral instability. .No history of patellofemoral instabilityن

Arthroscopy demonstrated a Postoperatively, the patient was postoperatively. At last follow-up, tially evaluated by the athletic train- displaced osteochondral fracture of placed in a hinged knee brace, approximately 2 years postopera- er, and placed in a knee immobiliz- the lateral femoral condyle measur- locked in extension, and he tively, the patient reported no er. ing 2 cm in diameter, and hemor- remained partial weight bearing for symptoms of instability, pain, or No history of injury or surgery rhage in the medial retinacular 6 weeks. Early range of motion was swelling. of either knee was reported. In region (Figure 2). Both menisci and instituted, initially at 0°-90°, and addition, no history of patello- ACL were intact. progressed to full passive range of Case 2 femoral instability in either knee Open reduction and internal fix- motion by 4 weeks. At 6 weeks the A 19-year-old female NCAA was noted prior to the current ation of the displaced osteochon- patient was advanced to weight division 1 soccer player presented injury. She was otherwise in good dral fracture was performed using bearing as tolerated, with full active with a large effusion and knee pain health. Arthrex Chondral Darts (Arthrex, range of motion while wearing a after sustaining a twisting injury to On physical examination, a Naples, Fla). A 4-cm medial para- dynamic lateral buttress patellar the left knee during a game the pre- large effusion was present and patellar arthrotomy was performed stabilizing brace. Strengthening vious day. The patient reported range of motion was limited sec- and primary repair of the medial exercises were begun 12 weeks immediate onset of pain and the ondary to pain. An arthrocentesis patellofemoral ligament was car- postoperatively, and the patient sensation that her “knee had gone was performed and 70 cc of san- ried out. returned to full activity 16 weeks out of place.” The patient was ini- guineous fluid was obtained. The

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patient had active and passive range cises were instituted with physical of motion of the knee from 0°- therapy. During this time, the 100°. The knee was maximally ten- patient exhibited no signs or symp- der over the medial boarder of the toms of loose bodies in the left patella and the medial femoral epi- knee. The patient returned to sports condyle. The knee was stable to 8 weeks following injury and at 2- varus and valgus stress at 0° and year follow-up the patient reported 30°. Lachman and anterior and pos- no recurrent dislocation of the left terior drawer tests were negative. patella. Pain occurred with lateral translation of the patella, and increased DISCUSSION asymmetric lateral patellar transla- Treatment goals for patients tion was noted at 30° of flexion. who have sustained a first-time Anteroposterior, lateral, and tunnel patella dislocation, include views of the left knee and Merchant restoration of normal pain-free views of both knees were normal. patellofemoral joint mechanics A diagnosis of acute lateral while minimizing the risk of patella dislocation was made. The recurrent subluxation and patel- patient was placed in a hinged knee la dislocation. brace locked in extension. Numerous retrospective 3 Magnetic resonance imaging studies exist in the literature, Figure 3: Case 2. Axial T2-weighted MRI demonstrating an effusion (black demonstrated an effusion and dis- which detail the success of arrow), disruption of the medial patellofemoral ligament (white arrow), and ruption of the medial patello- nonoperative1,6,7-10 and opera- osteochondral bone bruise of the lateral femoral condyle (small white arrows). femoral ligament at its insertions tive11-16 treatment of first-time on the medial border of the patella. patella dislocations. Compari- Magnetic resonance imaging also son of these studies is problem- erative treatment. One prospec- displaced osteochondral frac- revealed osteochondral bone bruis- atic given their retrospective tive randomized study17 ture is diagnosed by examina- es of the medial facet of the patella design, small sample sizes, dif- demonstrated equivalent results tion or imaging studies, it and lateral femoral condyle (Figure fering follow-up times, varied between operative and nonop- should be evaluated arthroscop- 3). The ACL, PCL, MCL, LCL, surgical techniques both erative treatment. Conservative ically and either reduced and medial and lateral menisci were between and within individual treatment has therefore become fixed or excised depending on intact. No evidence of a displaced studies, and heterogeneous our standard of care for initial the size of the lesion. Large treatment of first-time patellar unstable osteochondral frag- dislocations. ments typically require open Treatment goals...include restoration of Typical rehabilitation regi- reduction and internal fixation, mens include immobilization of whereas smaller fragments can normal pain-free patellofemoral joint the knee in extension for 2-3 be excised arthroscopically. mechanics while minimizing the risk of weeks. Range of motion and The incidence of chondral or strengthening can be instituted osteochondral injury following recurrent...patella dislocation. with the use of bracing to pro- acute patellar dislocation has tect against lateral displacement been reported to be as high as of the patella. Return to full 95% of cases.18 Furthermore, osteochondral fracture was noted. sample composition where pri- activity can typically be accom- standard radiographs have been The patient remained in the mary dislocators and patients plished 8-12 weeks from the reported to have a sensitivity of hinged knee brace, locked in exten- with previous history of time of injury. only 32% for identifying articu- sion and partial weight bearing for patellofemoral instability are Indications for acute surgi- lar injury.19 A majority of these 3 weeks. The patient was then grouped together (Table). cal intervention include unsta- articular injuries missed on placed in a dynamic lateral buttress Comparison of these studies ble osteochondral fractures and plain radiographs are non-dis- patellar stabilizing brace and range demonstrates equivalent results asymmetric unreduced lateral placed chondral and osteochon- of motion and strengthening exer- between operative and nonop- subluxation of the patella. If a dral fractures and of no clinical

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significance. However, if cation, history of symptoms of tion. Am J Sports Med. 2004; Buckley SL, Alexander AH. 32:1114-1121. Arthroscopic treatment of acute patients report loose-body patellofemoral subluxation 2. Conlan T, Garth WP Jr, Lemons patellar dislocations. Arthro- symptoms, despite negative prior to first-time dislocation, J. Evaluation of the medial soft- scopy. 1988; 4:267-271. radiographs and MRI, these and anatomic predisposition.1,6 tissue restraints of the extensor 13. Vainionpaa S, Laasonen E, symptoms should be further Regardless, no study to date mechanism of the knee. J Bone Silvennoinen T, Vasenius J, Joint Surg Am. 1993; 75:682- Rokkanen P. Acute dislocation investigated and treated, if nec- has demonstrated any disad- 693. of the patella. A prospective essary, with arthroscopy. vantage, in terms of surgical 3. Elias DA, White LM, Fithian review of operative treatment. J Bone Joint Surg Br. 1990; The disruption of the medial outcome, in delaying surgical DC. Acute lateral patellar dislocation at MR imaging: injury 72:366-369. patellofemoral ligament may repair until after a patient has patterns of medial patellar soft- 14. Avikainen VJ, Nikku RK, tissue restraints and osteochon- Seppanen-Lehmonen T. Adduc- dral injuries of the inferomedi- tor magnus tenodesis for patellar al patella. Radiology. 2002; dislocation. Technique and pre- 225:736-743. liminary results. Clin Orthop. Certain factors have been associated with 4. Virolainen H, Visuri T, Kuusela 1993; 297:12-16. T. Acute dislocation of the 15. Sallay PI, Poggi J, Speer KP, increased risk of recurrent dislocation patella: MR findings. Radio- Garrett WE. Acute dislocation logy. 1993; 189:243-246. of the patella. A correlative following first-time dislocation. 5. Kirsch M, Fitzgerald S, Fried- pathoanatomic study. Am J man H, Rogers LF. Transient Sports Med. 1996; 24:52-60. lateral patellar dislocation: 16. Nikku R, Nietosvaara Y, Kallio diagnosis with MR imaging. P, Aalto K, Michelsson JE. AJR Am J Roentgenol. 1993; Operative versus closed treat- occur as a midsubstance tear, an suffered a recurrent patella dis- 161:109-113. ment of primary dislocation of avulsion from the patella, or an location or subluxation versus 6. Hawkins RJ, Bell RH, Anisette the patella: similar 2-year results in 125 randomized avulsion from the medial operating after a first time dis- G. Acute patellar dislocations. The natural history. Am J patients. Acta Orthop Scand. femoral condyle. Finally, the location. Furthermore, the Sports Med. 1986; 14:117-120. 1997; 68:419-423. disruption may be multifocal in results of delayed proximal 7. Cofield RH, Bryan RS. Acute 17. Nomura E, Inoue M, Kurimura nature.3 An MRI is therefore realignment, performed in an dislocation of the patella: results M. Chondral and osteochondral injuries associated with acute useful for determining the loca- open or arthroscopic fashion, of conservative treatment. 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The long- literature. In retrospective and its associated risks. term results of nonoperative studies in which treatment was We therefore advocate for 10. Ahmad CS, Stein BE, Matuz D, management in 100 patients. Henry JH. Immediate surgical Am J Sports Med. 1997; nonoperative, recurrence rates nonoperative treatment of all repair of the medial patella sta- 25:213-217. range from 15%-44%.6,7 first-time patellar dislocations, bilizers for acute patellar dislocation. A review of eight cases. 20. Drez D, Edwards T, Williams Recurrence rates following unless a displaced osteochon- Am J Sports Med. 2000; C. Results of medial patello- 28:804-810. femoral ligament reconstruc- surgical intervention range dral fracture or an asymmetric tion in the treatment of patellar from 0%-17%.11,12 Certain fac- unreduced patella is noted. 11. Harilainen A, Sandelin J. dislocation. Arthroscopy. 2001; tors have been associated with Prospective long-term results of 17:298-306. operative treatment in primary increased risk of recurrent dis- REFERENCES dislocation of the patella. Knee 21. Halbrecht J. Arthroscopic patella realignment. An all-inside location following first-time 1. Fithian D, Paxton E, Stone M, et Surg Sports Traumatol Arthrosc. 1993; 1:100-103. technique. Arthroscopy. 2001; dislocation. These include al. Epidemiology and natural 17:940-945. history of acute patellar disloca- young age at the time of dislo- 12. Dainer RD, Barrack RL,

Section Editor: Darren L. Johnson, MD

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