Session IX - Tibia

Muscle Recovery After Tibial Diaphyseal Fracture

Charles M. Court-Brown, MD, FRCS Ed (Orth); Paul Gaston, MD, FRCS, Margaret M. McQueen, MD, FRCS Ed (Orth), Royal Infirmary of Edinburgh, Scotland, United Kingdom

Purpose: To investigate the effect of tibial diaphyseal fracture on the power of the reciprocal muscles in the lower limb and to determine which factors affect the return of muscle power and therefore limb function.

Methods: One hundred patients admitted between June 1994 and November 1996 with isolated fractures of the tibia and fibula were included in the study. Multiply injured patients and those with more than one fracture in the limb were excluded, as their functional recovery would be affected by the extent and severity of other injuries. Only patients with tibial fractures treated by intramedullary nailing were included in the study to negate the effect of employing different treatment methods. Fracture classification was undertaken by one surgeon to avoid inter-observer error. Open fractures were treated by debridement and immediate nailing followed by definitive soft tissue cover 36 ­ 48 hours later. Closed fractures were treated by immediate nailing.

Muscle function was assessed using a Biodex dynamometer. It was measured at 2, 6, 10, 14, 18, 26, 39 and 52 weeks after injury. Isokinetic peak torque, total work and average power were measured for knee flexion and extension, ankle dorsiflexion and plantarflexion and subtalar inversion and eversion. Each test consisted of six repetitions carried out as forcefully as possible at a slow speed (120 °/ second in the knee and 60°/ second in the ankle and subtalar joints). After a rest period the patients performed 15 repetitions at a fast speed (240°/ second in the knee and 120°/ second in the ankle and subtalar joints). The values of the injured extremity were expressed as a percentage of the value of the uninjured limb. Age, mode of injury, OTA fracture type, presence of an open wound and the Tscherne grade were all correlated with final limb function

Kruskal-Walis, Wilcoxon rank sum and Spearman rank correlation tests were used to analyse the data.

Results: Peak torque, total work and average power correlated very strongly with each other in both injured and uninjured limbs at each visit (Correlation co-efficients 0.62 ­ 0.99). The values at slow and fast speed also correlated with each other (Correlation co-efficients 0.83 ­ 0.98). To simplify the results we therefore present muscle recovery as measured by peak torque at the slow isokinetic speeds.

The knee flexors and extensors have about 40% of normal power two weeks after fracture, but this rises to between 75 ­ 85% at one year. Plantarflexion and subtalar inversion and eversion power are only about 10% of normal at two weeks but improve quickly such that they are relatively stronger than the knee musculature after 15 ­ 20weeks. By one year they have more than 90% of normal power.

Increasing age was associated with poorer muscle recovery, this being significant in the reciprocal ankle musculature. Patients up to 25 years of age regain full ankle dorsiflexion, but patients over 30 years only have 85% of ankle dorsiflexion power by one year. The OTA and Tscherne classifications correlated with final muscle function.

Discussion: This is the first study to analyze dynamic muscle function after tibial fracture. As muscle recovery largely determines function after tibial fracture it is important to understand the speed and extent of recovery. As expected, the quadriceps and hamstrings were not initially affected as much as the muscle groups crossing the fracture site. All muscle power improves rapidly for 15 ­ 20 weeks, and after this time the reciprocal knee muscles were relatively weaker than the other lower limb muscles. This confirms the need for active physical therapy for the hamstrings and quadriceps after tibial diaphyseal fracture.

Age was the most important determinant of outcome, and this observation is especially important when one considers the relatively narrow age band in any tibial fracture population.

Conclusions: Muscle recovery is relatively rapid for 15 ­ 20 weeks after tibial diaphyseal fracture with the muscles surrounding the fracture site initially being weaker than the reciprocal muscles around the knee. However, at one year it is the hamstrings and quadriceps that are weakest. The major determinant of final muscle power is patient age.