Seventeen males and ten females, aged 13 to 27 years, underwent operations for a lumbar hyperlordosis of neuromuscular origin responsible for major difficulties in sitting. In all patients, the sacrum was horizontal and associated in twenty-six cases with marked pelvic anteversion. Eleven patients were treated surgically by a posterior approach. The sixteen remaining patients had a preliminary discectomy, followed by posterior correction and fusion. Lumbar hyperlordosis was reduced from 8° to 77° between L1 and S1. The horizontal sacrum was partially reduced with an improvement from 8° to 50°. Consequently, patients recovered a comfortable sitting position. One patient died of respiratory complications six weeks after surgery.

L’hyperlordose lombaire d’origine neuro musculaire est rare et nécessite un traitement chirurgical afin de conserver une bonne station assise. Nous rapportons 27 cas de déformation sagittale avec hyperlordose chez des patients présentant des troubles neuro musculaires afin de déterminer les indications et les résultats de ces traitements. 17 patients étaient de sexe masculin et 10 de sexe féminin avec un âge s’échelonnant de 13 à 27 ans, tous opérés pour une hyperlordose lombaire d’origine neuro musculaire avec difficulté dans la position assise. Chez tous les patients le sacrum était horizontalisé et associé dans 26 cas sur 27 une antéversion pelvienne très marquée.11 patients ont été traitées par voie postérieure simple, les 16 restant ont été traités par voie postérieure avec correction et greffe après une discectomie préliminaire. L’hyperlordose lombaire a été réduite à 77° entre L1 et S1. L’horizontalisation du sacrum a été améliorée de façon partielle de 8 à 50°. Tous les patients ont retrouvé une position assise confortable, 1 patient est décédé de complications respiratoires six mois après la chirurgie. Le traitement chirurgical de ces déformations postérieures peut être réalisé par abord postérieur. Il est nécessaire d’analyser en pré-opératoire la balance rachidienne et pelvienne afin d’éviter une rétroversion iliaque et une perte du rôle de l’ischion dans la position assise.

The reported patients presented with a severe lumbar hyperlordosis which measured between 79° and 132° from L1 and S1 (Fig. 2). In 25 of 27 cases, bilateral hip flexion contractures of between 10° to 80° with asymmetrical contractures in twelve of 24 cases. In all cases, the sacrum was very horizontal, with sacral slopes from 59° to 107° while seated. Pelvic incidence values were relatively homogeneous in 26 cases and associated with pelvic anteversion with a “reversed” pelvic tilt between 1° and 62°. In one case, the pelvic incidence was 140° but the pelvic ring was not very tilted and pelvic tilt was only 33°.The detailed values of preoperative angular parameters are summarised in Table 1.

All patients were treated surgically by a posterior approach. In 16 cases, multiple-level lumbar discectomy and interbody fusion was performed through an anterior approach (thoracophrenolombotomy). In two cases (patients 11 and 12) an anterior osteosynthesis was done during the anterior approach. Except for one patient, the anterior and posterior procedure were performed separately, with a few days interval. Deformity correction was done with segmental instrumentation (CD Horizon-Medtronic Sofamor Danek Inc., TN, USA). Three patients were not felt to require sacral fixation because of a well balanced pelvis. Lumbar hyperlordosis correction was carried out using two rather different procedures. The first method used a small interval rod-hook construction placed at the apex of the curve. The small rod was approximated to the two principal rods by transverse traction devices (Fig. 3). This first technique was exclusively used in eight of 27 cases. The second method used pedicular screws placed at the apex of the curve and progressively pulled backward to reach the two principal rods (Fig. 4). This second technique was used exclusively in fourteen of 27 cases. The five remaining cases were treated by means of segmental instrumentation without a specific instrumented strategy. In all the cases, the frontal balance was obtained by distraction and compression manoeuvres applied to the spinal instrumentation. Fusion was carried out in all the cases with autologous bone graft. The postoperative course was uneventful in seventeen patients. One patient developed a thrombosis of the left common iliac vein secondary to Cockett’s Syndrome (abnormal compression of this vein by the right common iliac artery) with uncomplicated resolution of the thrombus following treatment. Three patients presented a limited zone of skin necrosis in the lumbar area with favourable outcome. In one of the two cases, the skin necrosis was associated with superficial soft tissue infection. One patient presented a deep haematoma requiring surgical treatment. Two patients had deep infections requiring removal of implants in one case. One patient had a partial osteosynthesis failure secondary to a lumbar pseudarthrosis and responsible for a progressive frontal imbalance. The outcome was favourable after repeat osteosynthesis and bone grafting. One patient died from respiratory failure six weeks after the surgical procedure. The postoperative course was pejorative despite continuous artificial ventilation in the intensive care unit. The details of surgical procedures and complications are reported in Table 2.

Functional status improved in 26 patients. Sagittal balance and sitting posture were improved. Lumbar hyperlordosis was reduced by 8° to 77° between L1 and S1. In 21 cases, sacral slope was partially reduced with an improvement by 8° to 50°. In 20 cases, pelvic anteversion improved with an improvement of the pelvic tilt from 2° to 47°. In fifteen cases, pelvic incidence was modified significantly. In one case whose initial pelvic incidence was 140° and initial pelvic tilt 33°, modification of pelvic alignment reduced pelvic incidence to 21° associated with a reduction of sacral slope from 107° to 84°. The final values of the angular parameters are reported in Table 2.

The follow-up range varies from 1 to 15 years. All patients’ functional status improved with a comfortable sitting posture and good sagittal balance. Comparison between preoperative and postoperative measurement showed a statistically significant variation of the lumbar lordosis, the sacral slope and pelvic tilt values; however, pelvic incidence was not modified significantly (Table 3). The comparison between patients surgically treated by posterior approach only (group 1) and patients treated by anterior and posterior approach (group 2) showed no difference between the two groups regarding preoperative angular parameters and postoperative angular parameters improvement (Table 4).

Analysis of pelvic position and modifications of lumbar-pelvic sagittal alignment is difficult, but a fundamental part of preoperative assessment. In a vast majority of cases, the lumbar hyperlordosis is responsible for pelvic “anteversion”, i.e. anterior flexion of the pelvic ring. Although analysis was done of lateral radiographs with the patient supine or sitting and not standing, pelvic “anteversion” was well visualised and pelvic tilt appeared reversed with a negative value. Sacral slope was high, sometimes >90° with a horizontal sacrum. In one case, there was a dissociation of the lumbar-pelvic sagittal balance with lumbar hyperlordosis responsible for a very horizontally positioned sacrum with a sacral slope of 107°. The pelvic “anteversion” in this case was related only to the sacrum and not the ilium (Fig. 8). Pelvic tilt measured 33° and lateral radiographs demonstrated the dissociation between a very horizontal sacrum and the rather “physiological” position of the iliac wings and the ischii. Our analysis of this lumbar-pelvic disorder was that there was rotation of the sacrum inside the pelvic ring through the sacroiliac joints. Frontal pelvic radiograph showed widening of the sacroiliac articular space. This progressively increased mobility of the sacroiliac joint was responsible for the increased pelvic incidence which measured 140° (Fig. 9a).

Our surgical strategy required analysis of the hyperkyphotic flexibility which was very difficult to assess. In many cases, the flexibility is poor because of the posterior muscles’ stiffness and spasticity. In these cases, it seemed necessary to us to perform preliminary anterior disc excisions. However, we think that extensive posterior soft-tissues release including the muscular and ligaments attachments as well as the ligamentum flavum between each posterior arch could provide the necessary correction and avoid the demanding anterior procedure. The advantage of a single posterior surgical procedure is to minimise the respiratory consequences of a long surgical procedure. Especially in cases of preoperative muscular impairment as in myopathy or in adult patients, phrenotomy could be responsible for severe respiratory dysfunction (as in case 26). The final correction obtained in eleven cases by the posterior approach only was satisfactory and allowed reduction of the horizontal sacral and lumbar lordosis which enabled patients to sit comfortably. The difference between combined anterior and posterior procedures and the posterior procedure alone was not statistically significant in terms of correction. Of course, the advantage of the combined anterior and posterior approach is to perform circumferential bone grafting. We experienced one case of lumbar pseudarthrosis after a single posterior approach but the outcome was good after repeat osteosynthesis and bone grafting by the posterior approach.