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POST TRAUMATIC OLD UNREDUCED POSTERIOR FRACTURE - DISLOCATION OF THE KNEE

Shreyash M Gujjar*, Sv Vaidya**, Alaric J Aroojis***
*Registrar; **Prof. and Chief of Unit; ***Lecturer; Dept. of Orthopaedics, Seth GS Medical College and King Edward VII Memorial Hospital, Parel, Mumbai - 400 012. India.

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A rare case of a post-traumatic, one year old, unreduced, posterior fracture dislocation of the knee with the fracture of the lateral femoral condyle (Hoffa’s fragment) is presented. The patient was treated by knee arthrodesis with a good functional result.

INTRODUCTION

Acute dislocations or fracture dislocations of the knee are true emergencies as they are often associated with neuro-vascular damage. [1] Hence, neglected fracture dislocations of the knee are rare entities. Posterior dislocations of the knee are less common as compared to anterior dislocations amounting to only 14.4% of all acute dislocations of the knee. [2] Dislocation of the knee may be associated with fracture of the proximal tibia. Approximately 13.6% of proximal tibial fractures are associated with severe ligamentous injuries and knee dislocations. [3] However, fractures of distal femur are rarely seen with knee dislocation. This case report is rare and not reported in literature.

CASE REPORT

A 28 year male patient sustained a vehicular accident while travelling as a pillon rider, one year ago, with injury to his partially flexed left knee. The force was directed upwards and backwards. The patient noticed a swelling of his left knee and was taken to a local health centre where he was operated upon (patellectomy) for probably a communited fracture of patella. The patient was immobilised in an above knee slab for a period of 6 weeks. The patient started weight bearing at the end of 8 weeks on a deformed, shortened and a painfully stiff knee. This was the time he was seen at our hospital with complains of pain, shortening, deformity and restriction of movements of the left knee.

No record was available to know either the initial status of the knee or what surgery was performed and whether he started walking on a dislocated knee or the deformity was progressive.

On examination, the tibia was dislocated posteriorly causing a grotesque deformity (Fig. 1). The anteromedial scar of previous surgery had healed well and a separate fragment was palpable posterolaterally. There was a flexion deformity of 20 degrees with further flexion up to 110 degrees. No abnormal anteroposterior or mediolateral mobility could be demonstrated. The distal pulsations were feeble but this did not affect the viability of the foot. There was no neurological damage. The patient had a painful, short-limb gait with poor endurance.

Fig 1	Preoperative photograph

Roentgenograms revealed posterior dislocation of the tibia with associated lateral Hoffa’s fracture of the femoral condyle which showed union. The patella was not visualised (Fig. 2). This and the vertical scar lead to our conjuncture that patellectomy was performed as initial surgery. Complete evaluation of the injury was possible with a 3-D computerized tomogram (Fig. 3).

Fig 2:	Preoperative roentgenograms (Hoffa's fragment seen)

 

Fig 2:	Preoperative 3-D CT Scan (Hoffa's fragment seen)

Arthrodesis was selected as the modality of treatment in this case and midline anterior approach was used. On exploration, the cruciate ligaments were found to be ruptured and the reduction was being hampered by the tightness of the posterior capsule and contracture of muscles (viz. gastrocnemius and popliteus).

The femoral and tibial cuts made the posterior soft tissue release easier. In view of the fact that there was already a compromise of the area of contact due to the associated displaced Hoffa’s fragment, we decided to make precise distal femoral and upper tibial cuts. This could be done conveniently with the help of total knee arthroplasty instrumentation (Howmedica total condylar). Despite the bone cuts, the tibia refused to translocate anteriorly. We released the posterior capsule along with release of both heads of the gastrocnemius and popliteus tendon. There was clearly, difficulty to relocate the tibia anteriorly hindered by posteriorly stretched capsule, because of united Hoffa’s fragment. This could only be brought anteriorly after debulking the Hoffa’s piece almost completely, so as to loosen the stretched capsule.

After achieving satisfactory bony contact, the arthrodesis was held with the help of Charnley’s compression clamps. The fixation was supplemented by a cylinder cast for 6 weeks. The patient was ambulated non-weight bearing for six weeks and union was confirmed on roentgenograms. The lower pin tract developed infection at around the end of 2 months, at which time the arthrodesis was satisfactory radiologically. Pins were removed and the patient was made to weight bear with cylinder cast. It was continued till the roentgenograms taken 4 months postoperatively showed sound solid union with good cross trabeculation (Fig. 4). Patient is presently walking without support or exoskeleton and is back to his occupation (Fig. 5).

 

Fig 4:	Latest postoperative roentgenogramsshowing at 4 months

 

Fig 5:	Photograph of patient walking without support at 4 months.

DISCUSSION

This is a case report of a rare condition which on review of literature does not show any similar neglected case of fracture dislocation of the knee.

The patient had an associated Hoffa’s fracture which classified according to AO classification falls in category 33.B 3.2. The Hoffa’s fragment was of the lateral femoral condyle and this lead to stretching of the posterior capsule which subsequently hindered reduction of the dislocation.

Posterior fracture dislocation of the knee is rare as compared to anterior fracture dislocation. [1,4-6] Posterior dislocation may be complete or incomplete, may be associated with fracture and injury is usually a direct trauma to the tibia or indirect i.e. acting by the force of body weight driving the thigh forward while the leg is semiflexed. In this case it was a result of direct trauma to the anterior aspect of the knee, resulting into comminuted fracture of the patelle, Hoffa’s fracture of the lateral condyle and a posterior dislocation of the tibia. The Hoffa’s fracture probably helped the dissipation of the force and prevented injury to the neurovascular structures in popliteal fossa. Kennedy in his series reported patellar tendon rupture associated with posterior dislocations. Good results of open reduction in acute dislocations have been reported by Thomsasen et al. [7] In contrast poor results have been reported after open reduction of old unreduced fracture dislocations of the knee even though articular surfaces may appear normal. [2]

The incidence of neurovascular damage associated with acute fracture dislocation of the knee is very high. The incidence of vascular damage (i.e. to popliteral artery) can range from as low as 10% [8] to 40%. [9] If the vascular supply is not established within 6 hours, the chances of developing complication like gangrene requiring amputation can be up to 72.5%. [8]

In such cases treated by open reduction, arthrodesis or arthroplasty are contemplated. In our case, taking into consideration the age, lifestyle and occupation of the patient it was decided to perform an arthrodesis. This was further justified by the presence of ruptured cruciate ligaments and the unhealthy articular surface.

In this case there was a strong solid ankylosis and patient had no interference with his day-to-day activities. Thus, arthrodesis proved to be the right choice.

REFERENCES

1. Freeman BL III. Old unreduced dislocations; Crenshaw AH (Ed), in Campbell’s Operative Orthopaedics, 8th Edition, Missouri, Mosby Year Book. 1992; 1374.
2. Speed K. Dislocations of the knee - in, A textbook of Fractures and Dislocations, 3rd Edition, Philadelphia, Lea and Febiger. 1935; 891.
3. More TM. Fracture dislocation of the knee. Clin Orthop May 1981; 156 : 128-40.
4. Jones RE, Smith EC, Bone GE. Vascular and orthopedic complications of knee dislocation. Surg Gynecol Obster Oct., 1979; 149 (4) : 554-8.
5. Schuster G. Dislocations of the knee joint. Fortschr Med March 27, 1980; 98 (12) : 415-8.
6. Zhang JS. Treatment of complications of complete dislocation of the knee joint. Chung Huo Wai Ko Tsa Chin July, 1989; 27 (7) : 430-1.
7. Thomasen PB, Rud B, Jensen UH. Stability and motion after traumatic dislocation of the knee. Acta Ortop Scand 1984; 55 : 278.
8. Montogomery JB. Dislocation of the knee. Orthop Clin North Am Jan., 1987; 18 (1) : 149-56.
9. Sisto DJ, Warren RF. Complete knee dislocation, A follow up study of operative treatment. Clin Orthop Sept., 1985; 198 : 94-101.

 

 

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