American Journal of Medical Genet ics 45:275 (1993)

Letter to the Editor

Complications of Elongating Intramedullary Rodding in Osteogenesis Irnperfecta

To the Editor:

Surgical treatment with fragmentation, realignment, and intramedullary rodding has greatly improved the functional prognosis in patients affected with severe osteogenesis imperfecta (01). Bailey-Dubow rods consist of an obturator and a sleeve and can elongate tele- scopically during bone growth, reducing the need for replacement. Our experience with this procedure is based on 16 patients (12 males, 4 females). Forty opera- tions were performed, 35 of which were primary rod- dings (femur 27, tibia 7, humerus 1). Age at the time of each primary rodding ranged from 2 to 11 years (aver- age 64/12 years). Follow up (referred to each primary operation) ranges from 6 months to 7 years (average 24/12 years). Complications were frequent.

Rod bending occurred twice after major trauma with fracture; these 2 rods were replaced.

Unscrewing of the T-shaped end from the sleeve oc- curred 3 times, always at the proximal end of the femur. Hip motion and trochanteric muscles contractions likely caused the unscrewing. Two were reoperated for this reason. We screwed the T-piece in again and then we scored the thread with snippers. Now we follow the same procedure at every rodding, just before assembling the rod, and no further unscrewing has occurred.

In one case, after trauma, the T end of an obturator broke at the inferior epiphysis of the femur and fell into the knee joint. So the obturator lost its anchoring at the bone surface and the rod did not elongate any further.

Failure to elongate with internal migration of the T ends of the rod occurred in 3 cases. We think that such a complication can be due to one or both of the following causes. First, there can be increased friction between obturator and sleeve, brought about by minimal damage and/or bowing, especially of the obturator, during surgi- cal manoeuvres. We recommend a very careful and deli- cate technique, in order to avoid any damage to the device, and an osteotomy as near as possible to the

mouth of the sleeve in order to introduce the obturator without effort. The second cause can be the fact that bone cortex is not able to bear the T ends of the rod. In fact, this complication always occurred in severely af- fected patients with very thin cortex and very porotic medulla bone (cystic appearance) that could not resist internal migration of the T end during bone growth.

Migration occurred in 2 cases. The first at the greater trochanter, required reoperation. The second occurred at the distal epiphysis of the tibia and consisted of a minimal displacement with no pain, no limping, no functional im- pairment. Reintervention was not necessary.

Nonunion occurred only in one case, at the superior osteotomy of a femur. Coxa vara is very frequent in osteogenesis imperfecta, due to weight bearing and to bone plasticity. During operation therefore superior end of the femur should be corrected in valgus. This is often neither easy nor possible. In this case “valgization” was not enough and the coxa vara, at this level, constituted an unfavourable biomechanical situation that hindered union. Except for this case, complete union at a normal rate was the rule.

In conclusion, complications are frequent (12 of 35 rods); 5 of these have required reoperation. No major complications (anesthetic or hemorrhagic complica- tions, infections, articular or growth plate damages) oc- curred. The complications encountered involved the hardware; these could be managed adequately and did not compromise the final result. We conclude that elon- gating Bailey-Dubow rod can be considered a reliable and effective procedure in 01, especially in growing pa- tients.

Pier Carlo Brunelli Paolo Novati Divisione di Ortopedia e

USSL 41-Ospedale dei Bambini Brescia, Italy

Paumatologia

&wived October 28, 1991; revision revised July 21, 1992. Address reprint requests to Dr. Pier Carlo Brunelli, Ospedale dei

Bambini “Umberto I,” Via Vittorio Emanuele 11, 25100 Brescia, Italy.

0 1993 Wiley-Liss, Inc.